1. Field of the Invention
The invention relates to optical character recognition systems, and more particularly, to an improved document transport and character scanner for an optical character recognition system.
2. History of the Prior Art
In prior art optical character recognition systems, a number of different techniques have been used for projecting an image of a character or line of characters to be recognized onto a matrix of photocells forming a retina. Such retinas are generally large, complex and expensive to maintain because of the optics required to project the image onto the retina and the probability of one or more individual photocells producing an improper response. The optical character recognition system of the present invention overcomes these disadvantages by employing a columnar retina including a plurality of photocells arranged in a single linear array across which images are scanned. The outputs from the individual photocells forming the columnar array are periodically sampled to produce electrical indicia from which a character is recognized.
The scanning systems of prior art optical character recognition systems have used cathode ray flying spot scanners, rotating lens systems and counter rotating prisms to scan the image of a character across a retina. Each of these devices, however, have inherent electrical and/or mechanical disadvantages due to their complexity as well as certain limitations due to the restrictions on scanning various document formats. Further problems have been encountered with using prior art systems to simultaneously sweep an illumination beam across a character array and scan the illuminated image while synchronously driving the transport system of the document being scanned. The invention employs scanning and transporting means which are held in synchronism and actuated by digitally controlled logic.